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GaryD

Aquaponics "Mythconceptions"

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gary, i now the difference between the two, the point i was making was the that the gammarus keep the AP systems clean enough to not have to deal with cleaning filters. their main population points are in the solid settling tanks, and in the gunk that falls from the net pots and collects in the bottoms of the troughs.

now would i use them in a purle aquaculture set up? probably not. the amounts of fish waste would be ridiculous... you'd need a large marsh type bio-filter like the wetlands of florida to give the scuds enough surface area to live and breed and also have enough space for the water to flow and allow the solids to settle to the bottom... although it is a big project, it's still fathomable...

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So true. My monitor and control system calls, texts and emails me and two other people if anything is the slightest bit off.

lol a recent build we did had delays with the electrician connecting the alarms. The monitoring gear was in but we were waiting for it to be connected. So I had the pleasure (for want of a better word) of getting up every 2 hours checking the system and the stock through the night in rotation with the new owners lol. When you have $80,000 of stock (worth $500,000 on the local market and 4 million on export) in the system you kind of what to be sure your money is ok.... In a new system later this year we can monitor and adjust everything (valves, pumps, dosers etc) on the iphone.... much more fun.

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Hi AE,

They will be back on the air a bit later today. I'm just in the process of resolving a web hosting issue and the web site that contains the programs will be available again.

You'll only need to click on the various links in the thread and you'll be moved to the original articles.

Let me know if you continue to experience access problems......but it should be sorted within the next few hours.

Gary

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Gary, your myth conception articles are fantastic! I mean just great- one sent me off on a rabbit trail for a week learning more about balancing the system by really understanding feed ratios!

I do have a question for you. you state

The good news about your convcerns about the need to add iron chelate, potassium and calcium is that, if you run your system pH at the lower end of the scale (say pH 6.0 – 6.3), it is not necessary to add those elements.

this is the first time I have ever heard this, can you effectively run your systems at this pH? also, some people like growing power use sand/gravel traps to remove their solids before the water is returned to the system. does this create an environment where denitrification will take place and therefore would these traps be unhealthy for a systems verses a clarifying tank or a solid removal filter than can be rinsed periodically?

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By the way, if I buy your online manuals can I print out hard copies so that I have the info after 1 year? I am a slow reader (LOL)!

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Hi AE,

The idea behind the subscription site is that you re-join every 12 months - and, in so doing, your manual remains current - and grows larger over time.

As things currently stand, the Online Urban Aquaponics Manual is not available in printed form. That may change as we have begun to look at packaging what we do in different ways.

On a different matter, where did you access that quote? I'd probably word that a little differently these days.

Gary

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Hi,

Gary, your myth conception articles are fantastic! I mean just great- one sent me off on a rabbit trail for a week learning more about balancing the system by really understanding feed ratios!

Thank you. I have a couple more on the way.

I do have a question for you. you state.....

"The good news about your convcerns about the need to add iron chelate, potassium and calcium is that, if you run your system pH at the lower end of the scale (say pH 6.0 – 6.3), it is not necessary to add those elements."

this is the first time I have ever heard this, can you effectively run your systems at this pH?

Yes, you can.......and pH has a significant impact on the availability of nutrients.

My interest in knowing where you got the quote (and I still can't find it) is premised on the fact that calcium (in some form) is probably the best way to ensure that you maintain your system above pH 6.0. Much below that and you risk a bio-filter crash.

I'd like to reword that sentence if you happen across it again again.

also, some people like growing power use sand/gravel traps to remove their solids before the water is returned to the system. does this create an environment where denitrification will take place and therefore would these traps be unhealthy for a systems verses a clarifying tank or a solid removal filter than can be rinsed periodically?

My personal preference is for dedicated mechanical and biological filtration devices......as distinct from trapping solids in media grow beds. You have far greater control of water quality if you capture and remove solid wastes and process them externally.

Systems that are fitted with such filtration are more productive, more resilient and more versatile than those are not.

Gary

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According to Portable Farms it seems that the application of Rock dust in aquaponics may solve the nutrient depletion problems of high feeder crops (such as fruiting vegetables) and I am concerned about its safety (see its chemical analysis below). I know that rock dust has been used by garden hobbyist forever but the addition of it in a closed-loop aquaponic system is slightly different and I fear that heavy metal absorption into plants and fish would not be desireable. To me this also represents a return to industrial agriculture sourcing of minerals and I find it unnecessary since one could simply use biochar as a source of potassium, calcium, and magnesium (the most common nutrients depleted in aquaponics). But none-the-less it seems to be "the new craze" in aquaponics and if I am to teach about it I would like to know from a soil/horticulture scientist(s) perspective if this “organic” source is potentially harmful.

Portable Farms application rate is 1 lb of the rock dust per 200 sq ft area of growing area:

post-8435-13795791162047_thumb.jpg

Any opinions?

post-8435-1379579116152_thumb.jpg

Edited by aquapon enthusiast
added new info (see edit history)

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So I guess I am confused- using a sand trap to capture sludge and solids that drain right back in the fish tank seems to be the same as just capturing all of it in the media beds- yes , you may not have to clean the solids from your beds but you still get all the harmful chemicals from dentrification via anaerobic digestion of the fish solids that will enter your fish tank (these would not be released if you had a clarifying tank/sludge filter that was cleaned often)- Growing powers cleans these sand traps monthy or longer until they get clogged- am I thinking about this the wrong way?

So just to reiterate, as long as you add Ca back to your system you can keep pH pretty low (usually you add Ca to Aquaponics using bases which will raise pH, in this case what source of Ca would be used (coral rock?).

Here it is Gary:

Mythconception #5 – Sustainability

gary says:

February 3, 2010 at 4:46 pm

Mike……..BSF larvae and duckweed are certainly a sustainable ration ingredient forsome species.

The good news about your convcerns about the need to add iron chelate, potassium and calcium is that, if you run your system pH at the lower end of the scale (say pH 6.0 – 6.3), it is not necessary to add those elements.

Duckweed is capable of bio-remediation but whether it would take up enough of the nutrients in a recirculating aquaponics system would require some controlled testing.

Fish wastes from an aquaponics system can be isolated and aerobically digested…….and the nutrient-rich liquor can then be decanted from the watery sludge. The liquor can be added back into the system and the sludge given to the worms or compost heap. Not only is this possible but, in my view, it’s desirable.

I imagine that worm tea could be added to an aquaponics system to provide another source of organic nutrients.

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Hi AE,

So I guess I am confused- using a sand trap to capture sludge and solids that drain right back in the fish tank seems to be the same as just capturing all of it in the media beds- yes , you may not have to clean the solids from your beds but you still get all the harmful chemicals from dentrification via anaerobic digestion of the fish solids that will enter your fish tank (these would not be released if you had a clarifying tank/sludge filter that was cleaned often)-

I wouldn't use a sand trap - they will clog eventually - and they run counter to my view that the solids are something to be harvested and re-used rather than seeing them as waste to be got rid of.

In fact, if we think in terms of the ultimate use to which they can be put, sedimentary wastes comprise fish poop - and also uneaten food. This uneaten food is 35 - 50% protein and, for chickens. ducks and quail, this is a nice little protein supplement - if you can get it to them before it starts to get on the nose.

Growing powers cleans these sand traps monthy or longer or when they get blocked....

I clean my filters every week......and I consider what I get out of the filters to be a harvest......which is then processed externally to retrieve all of the nutrients - which are then used in other parts of the system.

So just to reiterate, as long as you add Ca back to your system you can keep pH pretty low (usually you add Ca to Aquaponics using bases which will raise pH, in this case what source of Ca would be used (coral rock?).

Yes. I use calcium hydroxide (builder's lime)..

Ah, gotcha.....buried in the comments.....thanks for that.

It was a bit carelessly worded. I've changed it to read.....

The good news about your concerns about the need to add iron chelate, potassium and calcium is that, if you run your system pH at the lower end of the scale (say pH 6.0 - 6.3), it is not necessary to add those elements.....because they become more readily available to your plants at the lower pH.

You will probably still use calcium hydroxide (or similar) to maintain your pH above 6.0....or nitrification may decrease to the point where it stalls.

I wouldn't bother with rock dust. It was in common use, some years ago, but it's not necessary......and it just loads your grow beds up with sludge. There are liquid fertilisers (like Seasol for Australians and Maxicrop for Americans) that fill any nutrient gaps that might occur.

Gary

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Interesting about the rock dust. My outdoor AP system is in my front yard next to a busy street. It's a very dusty area as all winter the street is covered small crushed rock dust for traction. It's not until mid summer that we get enough rain to wash it clean. So instead of complaining this year, I'm going to think of the benefits to my AP system.

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Interesting point Gary, I imagine if you grow monoculture crops you would get an imbalance of nutrients over time if you didn't change the water so perhaps crop rotation in different tanks would help with that. I will have a unique situation where I will be growing a field crop next to my aquaponic set-up in a hoop house. Perhaps if I just use some of the water from the aquaponic tanks to irrigate the side-by-side field crop I will kill two birds with one stone- how: by using the aquaponic water containing the solids from the system to irrigate a small field crop and replacing the water with fresh water (that I would have used on the field crop)- in this scenerio, I will get rid of the solid waste from the beds and decrease the clogging problem, and replace fresh water in the system to balance the nutrients. Of course, you will have to re-balance your system accordingly by determining how many fish are required to support the plant growth in the bed as well as the plant growth in the field, but then you have a system that doesn't waste water, build up waste, and remains balanced!

I will let you know if it works well!

By the way Gary, I was told that you need to supplement your system with iron every two weeks at 2mg/L - is that correct? What should be the standard ppm concentration of iron in a system if tested routinely. Also, is there a minimum level of Nitrate that should be detectable in a system (say 10ppm) and anything above that level means you could add plants, and anything below that level may mean that you need to add more fish to have a balanced system?

Also, I am putting up a website and is it all right if I advertise this forum as well as your Urban Aquaponic manual ? I can send you the link so you can check it out!

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Hi AE,

Interesting point Gary, I imagine if you grow monoculture crops you would get an imbalance of nutrients over time if you didn't change the water so perhaps crop rotation in different tanks would help with that. I will have a unique situation where I will be growing a field crop next to my aquaponic set-up in a hoop house. Perhaps if I just use some of the water from the aquaponic tanks to irrigate the side-by-side field crop I will kill two birds with one stone- how: by using the aquaponic water containing the solids from the system to irrigate a small field crop and replacing the water with fresh water (that I would have used on the field crop)- in this scenerio, I will get rid of the solid waste from the beds and decrease the clogging problem, and replace fresh water in the system to balance the nutrients. Of course, you will have to re-balance your system accordingly by determining how many fish are required to support the plant growth in the bed as well as the plant growth in the field, but then you have a system that doesn't waste water, build up waste, and remains balanced!

I will let you know if it works well!

I have every confidence that it will work well. It addresses the waterwise "holy grail of aquaponics".......and your fish will love you for it. A genuine win-win.
By the way Gary, I was told that you need to supplement your system with iron every two weeks at 2mg/L - is that correct? What should be the standard ppm concentration of iron in a system if tested routinely. Also, is there a minimum level of Nitrate that should be detectable in a system (say 10ppm) and anything above that level means you could add plants, and anything below that level may mean that you need to add more fish to have a balanced system?
I don't worry too much about adding anything much unless the plants suggest that there's a shortage. I add chelated iron fairly infrequently....but then I run fairly low pH so what iron is in my system is more readily available that someone who was running a higher pH. Nitrates are never an issue because I'm usually running fairly high stocking densities.

If we're talking backyard production, let the condition of your plants be your guide. If you're going commercial, you'll need to be a bit more precise about things.

Also, I am putting up a website and is it all right if I advertise this forum as well as your Urban Aquaponic manual ? I can send you the link so you can check it out!
I'm happy to discuss any mutually beneficial arrangement......and I'd be happy to check out your site.

Gary

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